The torrent will flow for three days from the Glen Canyon Dam on the Arizona-Utah state line. It began Wednesday morning.
When the dam was built back in the 1960s, it destroyed sand bars down the Colorado River that used to be warm and muddy, reports CBS News correspondent Ben Tracy.
But the dam now traps silt and the river runs cold and clear through the canyon. The shift has helped speed the extinction of four fish species and push two others, including the endangered humpback chub, near the edge.
The sand bars in the Grand Canyon have significantly diminished in size and distribution as a result of the dam.
The spigot will unleash approximately 307,000 gallons per minute, reports Tracy.
The government agencies, including the Interior Department and Park Service, hope the flooding will stir up sediment and redistribute it through the canyon, which will get about four to five times the normal amount of water released from the dam during this week's flood.
They have done this twice before with mixed results, Tracy reports.